ᐅ Ventilation system with heat recovery, installation location temperature

Hello,

I have a central ventilation system with heat recovery installed in the attic of my new build. The attic is insulated but only has a small radiator that provides limited heating at a flow temperature of about 32°C (90°F). In winter, the attic temperature is around 14-15°C (57-59°F). Now my question:

Does it make sense to increase the temperature in the attic (for example, by installing larger radiators)? Would the system then operate more efficiently, meaning the temperature supplied to the rooms would increase and would I save heating energy as a result?

Thank you very much.

Best regards, Fabian

Whether it becomes more economical can only be determined based on the temperatures in the ventilation ducts.

We have our mechanical ventilation system installed in the uninsulated garage. Since it gets below 12°C (54°F) there in winter (12°C is the minimum temperature required by Pluggit for the installation location), we built a small insulated room around the ventilation unit. The buffer tank for hot water is also located in this room. This space is, of course, unheated as well, so it is a situation similar to yours.

I can’t imagine this being economical. In my opinion, the energy consumption of the additional heat source is higher than the gains from improving the operation of the mechanical ventilation system.

Even at an installation temperature of only 14-15°C (57-59°F), the temperature of the air entering the house is usually just 1-3 degrees lower than the temperature of the air being exhausted.

Example: Currently, our ventilation system exhausts air at 18°C (64°F), the outside temperature is 7°C (45°F), and after heat recovery the fresh air is warmed from 7°C to 16°C (61°F) before entering the house, while the outgoing air cools from 18°C to 11°C (52°F).

So, there is very little room to make the mechanical ventilation system more efficient. To increase the supply air temperature from 16°C to, say, 17°C (63°F), I would have to spend money on heating.

When I open the roof hatch, the temperature in the attic rises, and the temperature of the air being blown out increases to 20/21°C (68/70°F). When the hatch is closed and the attic temperature is only 15°C (59°F), the blown-out air temperature is 16°C (61°F). A 4°C (7°F) difference?!

I have an idea. Since the radiator is located close to the ventilation system, I could install a heating coil inside the ventilation unit. My father is a stainless steel welder, so that wouldn’t be a problem for him. This should increase the efficiency, right?

Hi,

Vwgolfcabrio schrieb:
Hello,

In my new build, I have a central ventilation system with heat recovery located in the attic. The attic is insulated but only has a small heater that provides little warmth with a flow temperature of about 32°C (90°F). In winter, the attic temperature is around 14-15°C (57-59°F). Now my question:
Would it make sense to increase the temperature in the attic (e.g., by installing larger heaters)? Would the system then operate more efficiently—that is, would the temperature delivered to the rooms be higher and could I save heating energy?
Thank you very much.

Best regards, Fabian

Why should that help? The system includes heat recovery, so it recovers heat from the exhaust air and supplies it to the incoming air. The ambient temperature around the system hardly matters. It just needs to be frost-free so that condensate can be drained properly. Everything else is almost irrelevant.
Of course, well-insulated ventilation ducts are a prerequisite!

Best regards,

Andreas